Insulated casing



2 n mf Patented June v, 1948 UNITED STATES l PATENT OFFICE I 2,443,605 i I INSULATED CASING Cornelis de Lange, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application March 23, 1943, Serial No. 480,192 In the Netherlands June 26,1941

Section 1, Public Law 690, August 8, 1946 Patent expires June 26, 19.61

7 claims. (ci. 17e-74) This invention relates to an insulating casing or envelope for an electric component such as condenser or a resistance, which is closed by means of a cover of ceramic material through which pass one or more connecting leads of electrodes arranged inside the envelope, which cover is coated, at least partly, with a iayerof glaze.

The use of ceramic material for obturating such envelopes at one or at both ends offers various advantages. The ingredients are cheap and the workplaces can easily be manufactured in mass-production. Those parts which are to be connected with metallic components, for example, the envelope, itself, can easily be metallized so as to allow soldering. In those cases wherein the dielectric properties have to come up to high requirements, the latter can easily be complied with by the choice of the ceramic material.

The use of ceramic material entails, however; drawbacks which arise from the nature of the surface, lfor this surface is rough and somewhat porous sc that moisture can be easily taken up from the surroundings with the result, however, that the insulation resistance along the surface is reduced so that along this so-called surface leakage path, a leakage current may be produced. Furthermore, due to the roughened surface impurities can easily adhere to the surface, which likewise results in that the insulation resistance is reduced. In order to avoid the above-mentioned drawbacks, the surface of the workpiece consisting of ceramic material is glazed.

The present invention has for its object to give the cover for an envelope for electric components such a shape that on the one hand the surface leakage path between the 'parts of different potentials whieh are attached to the cover is lengthened in a simple manner and, on the other hand, the insulation resistance obtained with the aid of a layer of glaze is raised to the highest possible value. According to the invention this result is obtained owing to the fact that the leading-through apertures are widened at the ends so that in the cover an annular recess is formed in which a coating of glaze is provided. It should be considered that the surface leakage at least partly, with glaze. .However, if a cover which has the shape of an ordinary dat disc is placed in a glazing furnace, it is impossible directly to glaze both' the top and the bottom surface of the disc, for the latter surface lies on the -bottom of the furnace so that the glaze naterlal cannot reach this surface (dead surace).

The invention affords a construction which ds not only create long surface leakage paths, but wherein also the above-mentioned drawback is cbviated by the use of a layer of glaze for both leakage paths.

With the coveraccording to the invention, which exhibits an Iannual recess around the leading-through aperture, room has, so to speak, been gained so that the surface leakage path itself is lengthened whilst that portion of the leakage path which is present in the said recess can also be glazed since it does not rest on the bottom of the glazing furnace.

In one advantageous form of construction, the recess around the leading-through aperture is widened to such an extent that the disc which constitutes the cover has the shape of an inverted dish.

The invention will be explained hereinafter in detail with reference to the accompanying drawing, wherein:

Fig. 1 diagrammatically represents, by way of example, a flrstfrm of construction, whilst Fig. 2 represents, as a second form of construction, a condenser which is formed as a leadingthrough condenser.

A metal cylinder l, which is shown in section in Fig. 1, contains an electric component, for example a condenser, and is closed by a cover 2 current may flow along two different sides so that vfrom a. member with a determined potential to another member there are two surface leakage paths of which the one extends along the top surface and the other along the bottom surface of the cover. It is therefore essential to make both paths as favorable as possible. To that end, it is desirable to coat both leakage paths,

of ceramic material which has apertures 3 and I through which pass leading-in conductors 5 and Bwhich are iixed therein by means of cement or solder.

The layer of glaze present on the ceramic cover is indicated by a hatched area at the circumference. On the underside of the cover, there is no glaze on the surface which enters into contact with the bottom of the glazing furnace but the layer of glaze is present on the walls of annular recesses 1 and 8 which are formed owing 'to the fact that the lower ends of the leading-through apertures 3 and 4 are widened. As on the upperside of the cover, the surface leakage paths between the leading-through conductors 5 and 6 and to the metal cylinder I consequently partly extend over glaze. It is very easy to widen the leading-through apertures in the manufacture -since this is Aeifected simultaneously with the pro-y duction of the latter. with the aid of a single former.' i

A condenser such as shown in F18. 2 may be incorporated in filter systems for leading highfrequency oscillations away from a main current conductor.

Flor the envelope use is made of a copper tube 9 which is obturated at both ends by ceramic covers lo and lo' which are both dish-shaped since the widening of the leading-through aperture has been continued so far that there only remains a rim I I. It appears from the gure that a disc of the shape shown is advantageous in the glazing operation since only a small surface, viz. that of the end of the rim II, is not glazed. (Here, again. the places which are provided with a layer of glaze are indicated by hatched areas.) For securing the cover to the envelope o, the outer circumference of the rim Il is silver-plated so as to allow solderingas is indicated by a dashline. The condenser C.. which is present inside the envelope, is of the wound type which comprises in the known manner short-circuiting plates I2 and I2' in order to keep the windings.

which are diagrammatically indicated by lines of a material which gives rise to small high- `frequency losses.

By a cylinder I6 of the same insulating material, the wound condenser is separated from the envelope. The one electrode of the condenser is connected to the central pin I4 by means 'of asoldered `ioint Il. The solder I8 which connects the cover l withthe envelope' 9, also establishes the connection between the electrode I2, I3? and the envelope. The pin Il is secured inthe aperture I9 of the cover I0 by means of solder 20. In a similar manner, the other end of the pin passes .through the cover Ill.

What is claimed is: y

1. A casing4 for an electrical device subjected to high voltage in the normal operation thereof comprising a metallic casing' electrically connected to one terminal of saiddevice, a metallic tube of greater length than said casingco'ncentrically located therein and electrically connected to Ithe other terminal of said device, an insulating cover of ceramic material with a portion of its surface glazed and located at each end of said casing, said cover having a central aperture for the passage of said tube therethrough, said cover having an inside recessed portion with its walls glazed and an unglazed' portion, a metallic coating covering a portion' of said unglazed portion, each one of said insulating covers soldered at the metallicrcoating portion and to the end of said casing.

2. A casing for an electrical vdevice subjected to high voltage in the normal operation thereof comprising a cylindrical metallic casing servingr as one terminal of said electrical device, a metallic tube of greater length'than said casing and serving as the other terminal of said electrical device located concentrically within said casing, an insulating cover of ceramic material located at each end of said casing with an aperture therein for retaining said metallic tube, said insulating cover having a recessed portion with its walls glazed and an unglazed portion, a. metallic coating covering a portion of said unglazed portion, each one of said insulating covers soldered at the metallic coating portion to an end of said cylindrical casing and to an end of said metallic tube.

3. A casing for an electrical unit of the high voltage type having at least two terminals, a Y

central metallic tube of greater length than said unit and arranged to extend beyond each end of said unit, one of the terminals being electrically connected to said central metallic tube. an insulating tube interposed between said metallic tube and said unit, said insulating tube extending beyond the body of the said unit to insulate the other terminal therefrom. an outer metallic member for enclosing said unit, the other terminal being electrically. connected to lsaid outer metallic member,- and means vconstituting covers of ceramic material for closing the casing located at the ends of said unit, said cover having a central aperture and an inside recess with its walls glazed and an unglazed portion, a part of the said unglazed portion being soldered to the said metallic tube.

4. A casing for an electrical device subjected to -a high voltage in the norm-a1 operation comprising a cylindrical metallic casing., a circuit element within said casing and having one electrode electrically connected to the said casin-g, a metallic tubular member located concentrically with theV said casing-and having a greater length than .the said casing, said tubular member being electrically connected to said circuit element and serving -as the other electrode thereof, an insulating cover of ceramic material located at each end of said casing, said covers being each provided with a central aperature for retaining said tube, each of said insulating covers having an inside recessed portion Wit-h its walls glazed and an unglazed portion, a metallic coating covering a partof each ofthe said unglazed portions, each of said insulating covers being respectively soldered at certainv of the said parts to the said casing and the said tube.

5. A casing for a high voltage circuit element mounted on a central support, comprising a metallic casing, two like ceramic covers formed with a central aperature and an annular recess surrounding the aperture, the outside cover surfaces and the surfaces of the said recess being coated with -a glazed layer, the ends of the said support passing through the said. central apere tures and being soldered to said cover, said covers also being soldered to said casing, and means for electrically connecting the said element to the said support and to the said casing. A

6. A casing for an electrical device subjected to high voltage in the normal operation thereof, comprising a metallic tubular casing, a cover portion of ceramic material having a glazed outer surface and an unglazed inner portion adapted to intert with said tubular casing at one end thereof, and a pin member serving as a connecting lead for said electrical device, said cov'er portion provided with an aperture deiining an inner unglazed surface Iportion for passing said pin 'through .from said electrical device, the inner portion of said cover having an annular recessed portion surrounding the aperture with Walls spaced apart from said pin and glazed to increase the surface insulation resistance, and the unglazed surface portion of said Japerture being soldered to the ends of said pin member,

7. A'casing for an electrical device subjected to high. voltage in the normal operation thereof, comprising a tubular metallic casing, two ceramic covers adapted to intert with said casing and partially enclosing said casing, a pin member axially extending through said casing providing connections for said electrical device, each oisaid covers provided with an aperture for passing said pin member through iromrsaid electrical device, said cover provided with an inner annular recessed portion surrounding said aperture, the outer and' inner surface portions of said cover being coated with a glazed layer to increase the insulation resistance o! said electrical device, 4and said pin member being secured 10 to the wall portion of said aperture.

CORNELIS nx LANGE.

lfile of this patent:

Number Number UNITED STATES PATENTS Name Date Gaebel et al July 4, 1939 Schoonenberg Aug. 29, 1939 Gerecke et al May 14, 1940 Stevens ,Aug. 4. 1942 Cox 1 Feb. 9, 1943 FOREIGN PATENTS Country Date Switzerland Apr. 1, 1942 GreatBritain Apr. 23, 1936 France Mar. 13, 1939v 

